shows the surface SEM micrographs of undoped and CuO-doped BNKT ceramics sintered at 975 for 2 h in air.Undoped samples exhibit little grain growth with poor densification at such low Ts,however,both the average grain size and relative density increase up to 1.14 m and 96% respectively,by adding excess CuO even as low as 1 mol%. further increasa in the average of CuO aid only results in slight enhancement in the average grain size. It should be noted tat the secondary phases are observed at grain boundaries and corners as indicated by arrows on the figures.which strongly suggests the presence of a liquid phase during sintering similarly to CuO added KNN ceramics.However,XRD analysis detected little secondary phases,implying that the observed unwanted phase between grains is amorphous.